Since the advent of motorized vehicles it has been desirable to measure and display various characteristics of vehicle performance and operation. While there are many different types of engine-driven vehicles, including automobiles, trucks, aircraft, and boats, the nature of the parameters to be measured and displayed is fundamentally similar, and many are common to all of the aforementioned applications, such as, for example, vehicle speed, engine speed, engine oil pressure, coolant temperature, battery voltage, and remaining fuel.
The mechanism for measuring and displaying these and other parameters generally includes a sender and a gauge attached thereto. The sender measures the specific parameter of interest and converts that quantity into an electrical signal. The gauge receives the electrical signal generated by the sender and converts it into some form of human-readable display, such as, for example, a pointer movement across a printed dial face.
Historically, these systems have enjoyed very widespread use and acceptance. Most engine-driven vehicles have at least one such sender and gauge pair, and many, such as large boats, have upwards of seven. However, despite their popularity, traditional sender and gauge systems present certain inherent drawbacks, especially when utilized in a large vehicle. Senders are typically located on or near the engine, while gauges are usually located near the vehicle operator. Such an arrangement may be adequate for smaller vehicles like automobiles, but trucks, aircraft, yachts, and other large vehicles often distance the operator from the engine. Thus the wires between the senders and their respective gauges must extend for long distances throughout the body of the vehicle. Furthermore, the arrangement of one wire for each sender and gauge pair means that a substantial number of wires must extend across the vehicle, which takes up space and adds weight. Also, sender signals typically present information via varying voltages, currents, resistances, or even by means of digitally encoded information. When wires carrying a variety of signals are bundled together across significant distances, there is a potential for crosstalk between adjacent wires, and reliability can decrease proportionately as the quantity of wire in the vehicle increases.
Aside from the physical hardships, there are additional electrical issues regarding gauge responsiveness in the traditional sender and gauge pair system. Since each pair is separate from the other pairs, it is impossible to coordinate between related gauges, such as, for example, running an hourmeter only when the tachometer indicates that the engine is operating above some minimal RPM level. Furthermore, each gauge must be specifically configured to interpret the signal received from the sender, such that it is incapable of being used with a sender of a different scale. For example, traditional fuel senders include, among others, senders which run linearly from 0 to 90 ohms across an Empty to Full range, as well as senders which run linearly from 240 to 33 ohms across the same range. A conventional fuel gauge associates specific ohm readings from the sender, such as, for example, 45 ohms, with specific fuel quantities. Consequently, a gauge which is designed to operate with the 0 to 90 ohm sender will give inaccurate readings when used with a 240 to 33 ohm sender. This characteristic applies to all traditional sender and gauge pairs, resulting in inconvenience, expense, and even re-work when gauges and senders are not properly matched.
It would thus be desirable to have a means for concentrating one or more analog or digital sender signals into a single, reliable digital data signal. The present invention is directed at achieving these objectives.